Earth-53
The second Earth in this Multiverse and arguably one of the biggest it probably would have been just like the League's world except one tiny historical change happened.
You see sometime before recorded history all of humanity lived in one big city called Babel however a meteor struck it confusing their languages and forcing them to go their own way.
However they soon discovered that this meteor turned exactly half of all the animal species on the Earth humanoid.
Despite the early shock the creatures all got along fine until the Egyptians started worshipping cats soon making them and humans the most powerful creatures on the globe.
The jealousy of the dogs lead to a bloody interspecies war in BCE 1440 which didn't stop until BCE 1402 when the Egyptians bribed the dogs to stop.
While another such skirmish wouldn't happen for centuries battles of this type were around the world and animals generally were ruled by one of their own number although some creatures tended to align themselves with other countries. For example mice tended to like the Hebrews and pigs began joining the nation when they realized they wouldn't eat them.
Later in in Rome they began enslaving dogs something that lead to the Spartacus slave dog revolt however all but one member of the revolt (Orlando who was one of the only two cats involved) was killed one other cat involved was Spartacus' lover who ran away with their child…a dog/cat hybrid that eventually would take part in the fight known as Ragnarok.
This was a problem for the cult known as Kobra who had started the whole dog/cat feud as a way to cover up their criminal activities as well as their long-term plot to take over the world.
A significant development o this Earth came in 1558 when Queen Gloriana was able to put a temporary truce between all humanoid species and thus no wars happened for that time until her death.
However after her death her insane Puritan nephew King Jacob began a ruthless persecution of the Fairy Race he was assassinated twenty years later by Prospero's Men and a time displaced superhero for his crimes.
In 1775 the British Colonists in America rebelled against England and formed their own country which would become the birthplace of what gave the thing that gives the modern age what makes it the most dangerous time of this Earth.
Later in 1898 Martians attacked Earth but were destroyed by the "Common Cold" in reality though that was a lie it actually was biological warfare that killed them
In 1899 Alan Quartermain (having recently gained immortality) and Mina Murry did "some things" and nine months later on New Year's Eve 1900 produced a dog/cat hybrid.
They left the child at a Catholic Church and while it was later adopted by French Nobles Kobra got wind of it and hurriedly produced propaganda saying that it was scientifically impossible for cats and dogs to mate in 1904 ironically an occultist named Oliver Haddo found this out but only his cult believed him.
Kobra then convinced the child that he was the product of incest, as a way to explain his appearance.
The child however turned out to be an unaging Century Baby and at some point took the name of axel Brass and fought crime with a team of other Century Babies although they did their work in secret.
Shortly after WWI a superhero with flight called Air Ace became the first open hero and later inspired a wave of costumed heroes such as Hawk of the Alleyways and The Cloak of Night.
This was the beginning of something that gave the Modern Age it's inhuman danger and inspired other countries to try and build group of heroes to keep their own boarders safe such as India's The Unclean.
In WWII Hynkel's armies put the other countries strength to the test as the world struggled to keep him from taking it over.
In the sixties dozens of people showed up that were apparently born with superhuman powers while they had shown up before they never had in these numbers.
These creatures (termed Mutants) could offer no clue as to where the Mutant gene originates but they did find out that animal hybrids stand a better chance of getting the gene then normal people/animals do.
Costumed heroes became popular again in the Nineties with the coming of an alien a survivor from a doomed planet who became a superhero called Supergator (due to him being in fact a humanoid alligator) along with him was billionaire Bruce Wayne who spent his nights as the evil vanquishing Battiger.
In 1994 professor Curtis Connors lead an expedition to an underwater city called Rapture which sadly ended with him being the only survivor due to "monstrous beings in diving suits" and "hideously deformed beings" meanwhile somewhere in the country a child prodigy was born.
The child which shall remain nameless at this time when he was 13 attempted a dangerous experiment with intrinsic fields which gave Dogter Mutthattan his powers.
Hoping to get the power to help people he used the process on himself, but six weeks later when he returned he turned into an insane psychopath calling himself Dr. and reveals that what the Field gives you is completely random and what it gave him was a new body and personality to match.
Dr. became what could be he most dangerous terrorist mind
Due to this Dr. began using his massive intellect and immunity to harm to as he put it "cause so much anarchy and chaos the whole world see me as the very essence of madness itself."
Two years later he discovered the Multiverse and became obsessed with the idea of controlling it he called it Conspiracy 13 due to his goal to "install 13 cells of it on each Earth."
Interestingly enough despite this being Dr.'s home the League of the Multiverse never visited this Earth.
On a closing note about this Earth superheroes would still be there well into the 30th century and because of the abnormally high level of superheroes and villains Dr. referred to it as being " one of the hardest conquests I'll have."